Vox AD30vt amp problems...

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dwebb3
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Vox AD30vt amp problems...

Post by dwebb3 » April 21st, 2009, 6:33 am

soooo last night i was at band practice and i had to use my little 30 watt vox amp.My bandmate was using a half stack for the second guitar so i had to turn the vox all the way up(and it was the first time i've ever done that...).So we start practicing and the little amp measures up with the half. Were about an hour in and right in the middle of the song the sound just cuts of....We tried everything, seeing if it wasnt plugged in, changing the guitar, changing the cable, checking if we changed a setting on accident but to no avail...When i got home i tried again because we thought it was over heated and it still didnt work. But....when i plug headphones into the amp it works fine...so can anyone give me a diagnosis?

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Gabba Gabba Hey
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Re: Vox AD30vt amp problems...

Post by Gabba Gabba Hey » April 21st, 2009, 7:43 am

Maybe a speaker wire came loose? You'll probably have to open it up to check ... hopefully it's something simple like that.

dwebb3
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Re: Vox AD30vt amp problems...

Post by dwebb3 » April 21st, 2009, 7:48 am

Gabba Gabba Hey wrote:Maybe a speaker wire came loose? You'll probably have to open it up to check ... hopefully it's something simple like that.
Thank you...i've been waiting for someone to reply...lol

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kent_eh
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Re: Vox AD30vt amp problems...

Post by kent_eh » April 21st, 2009, 3:46 pm

It's possible that one of the wires in the speaker that goes from the terminal strip to the voice coil broke, or possibly the coil failed.
Do you have a multimeter and a soldering iron?
And do you know how to use them?

You said this amp has never been pushed to those levels before, right?

BTW, how new is this amp? does it have any warranty left?
Thank you...i've been waiting for someone to reply...lol
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BluezOldy
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Re: Vox AD30vt amp problems...

Post by BluezOldy » April 21st, 2009, 7:49 pm

It might be worth checking out the Valvetronix forum:

http://www.valvetronix.net/forums/

Mine's gone wonky a couple of times and I've had to follow the reset procedure in the manual.

Also a common complaint is that they have very cheap input jacks in them which dry out and corrode. This can be fixed with proper electrical contact cleaner (not WD40 type products).

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IbanezJunkie
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Re: Vox AD30vt amp problems...

Post by IbanezJunkie » April 24th, 2009, 3:49 am

tubes blown?
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kent_eh
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Re: Vox AD30vt amp problems...

Post by kent_eh » April 24th, 2009, 5:43 am

I just took a look at the schematic and it could easily be something in the power amp section. The headphone output comes off before the power amp section.

But, if it isn't something simple like a speaker wire come loose, you might want to check your warranty status.
Unless, of course you like to fiddle with electronics at the circuit level (like some of us do).
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TrippingCobras
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Re: Vox AD30vt amp problems...

Post by TrippingCobras » June 30th, 2010, 12:54 pm

I have one of these as well, they are prone to having issues with the amplifier portion of the amp. Your headphones work because you are using the preamp section of the amplifier. More than likely the problem lies with the LM3886 audio power amplifier; don't worry, it is a single chip.
If you are capable of soldering, you have to remove the old chip which is 11 pins. This can be a real pain to desolder. I use braided copper to remove the old solder. I haven't had to repair mine yet, but I believe you can get these chips for about $6 + shipping and handling. Just do an internet search, these are fairly common. http://www.national.com/ds/LM/LM3886.pdf

Obviously I can't completely troubleshoot your amp without first taking a look, but this should point you in the right direction.

Best regards

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